JPH09229628A - Position sensing method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish precise position sensing by exerting maximum averaging effect when a lattice marking is illuminated by a light flux containing a plurality of wavelength components. SOLUTION: The position ΔX'n of each lattice marking is wavelength by wavelength sensed by a circuit SAn and circuit CAn (n=1, 2, 3) from the photo- quantity signals IAn, IBn (n=1, 2, 3) obtained by the interferential alignment method based upon the ON'th order sensing method. The circuit SAn calculates the step equivalent amount δn wavelength by wavelength as the surplus for each half-wave of the incident beam around the mark surface at a step on the basis of the design data of the lattice marking and a change associate with the relative scan of the photo-quantity signals IAn, IBn. A circuit SS takes weighted average of the positions of the lattice marking sensed with different wavelengths in such a way that one whose step equivalent amount is nearer one quarter of each wavelength around the mark surface of the incident beam is given a greater weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting method and an apparatus therefor, and more particularly, to a mask pattern and a photosensitive substrate in an exposure apparatus used in a photolithography process for manufacturing a semiconductor device or the like. The present invention relates to a position detection method and device suitable for use in detecting a mark position during relative alignment.

[0002]

2. Description of the Related Art For example, in a photolithography process for manufacturing a semiconductor device, a liquid crystal display device, a thin film magnetic head, or the like, a photomask or reticle (hereinafter, collectively referred to as "reticle") on which a transfer pattern is formed is used. There is used an exposure apparatus that transfers an image onto a wafer (or a photosensitive substrate such as a glass plate) coated with a photoresist by a projection exposure method or a proximity exposure method via a projection optical system.

In such an exposure apparatus, it is necessary to perform alignment of the reticle and the wafer with high accuracy prior to exposure. In order to perform this alignment, it was formed on the wafer in the previous process (exposure transfer)
The formed position detection mark (alignment mark) is formed. By detecting the position of this alignment mark, the accurate position of the wafer (circuit pattern on the wafer) can be detected.

In recent years, an alignment mark on a wafer (or a reticle) is formed into a one-dimensional or two-dimensional lattice shape having irregularities, and two coherent beams symmetrically inclined in the periodic direction are projected on the lattice mark. A method of interfering two diffracted light components generated in the same direction from the grating mark to detect the position or positional deviation of the grating mark in the periodic direction (hereinafter referred to as “interferential alignment method”) is, for example, (A) It has been proposed in Japanese Laid-Open Patent Application No. 61-208220, (B) Japanese Laid-Open Patent Application No. 61-215905, and the like. Of these, publication (A) discloses a homodyne system in which the frequencies of two symmetrical coherent beams are the same, and publication (B) describes
A heterodyne system in which a constant frequency difference is provided between two symmetrical coherent beams is disclosed.

Further, a heterodyne type position detecting device is applied to a TTR (through-the-reticle) alignment system and a TTL (through-the-lens) alignment system in a reduction projection exposure apparatus, as disclosed in (C) JP-A-2-227602. , (D) JP-A-3-2504. In the heterodyne method disclosed in these publications (C) and (D), the two acousto-optic modulators (AOMs) are provided with He.
-Ne laser beams are made incident at the same time, each AOM is driven by a high frequency drive signal (80 MHz for one side and 79.975 MHz for the other) having a frequency difference of, for example, 25 KHz, and 25 KH between the diffracted beams emitted from each AOM.
The frequency difference of z is given. The two diffracted beams are used as a pair of light-transmitting beams for irradiating the grating mark on the wafer or the reticle with a predetermined crossing angle.

In the heterodyne system, the frequency difference (25 KHz) between the two transmitted beams is used as a reference AC signal, and the interference light (beat light) of the two diffracted light components generated from the grating mark is photoelectrically detected. The phase difference from the reference AC signal is measured and detected as the amount of positional deviation from the reference point in the periodic direction of the lattice mark.

The optical system for realizing the interferential alignment method can be roughly divided into three types depending on the method of injecting the coherent beam (laser beam) to the grating mark.

First, two laser beams are incident from ± N-order directions which are symmetrical with respect to the period (= P) of the grating mark, and the interference of the period of amplitude P / N is caused on the grating mark. A diffracted light that forms a fringe and is reflected / diffracted vertically upward from this (combined light flux of ± N-order diffracted light of both incident lights: N is a natural number) is received, and the position of the grating mark is detected based on the change in the light amount. Type (hereinafter, abbreviated as “± Nth order detection method”).

Secondly, the two beams are made incident symmetrically from the ± N / 2 quadratic direction with respect to the period of the grating mark to form an interference fringe having an amplitude period of 2P / N on the grating mark, and one of the two beams is formed. A combined light flux of the 0th order diffracted light (regular reflection light) of the (first) incident light and the Nth order diffracted light of the other (second) incident light, the 0th order diffracted light of the second incident light, and the first incident light Of the N-th order diffracted light is received independently, and the average value of the two detection positions obtained from each phase of the light amount change of both light beams is used as the position of the lattice mark (hereinafter, referred to as "0N-order detection method"). "" Is abbreviated)
It is.

The third is that only one beam is incident on the grating mark and two ± N-order diffracted lights that are reflected and diffracted are imaged on the reference grating, and from the change in the amount of transmitted light from the reference grating, This is a type for detecting the position of a lattice mark (hereinafter, abbreviated as "reference lattice method").

In principle, there is no difference in the lattice mark detection positions by these three methods. However, ±
The Nth-order detection method and the 0Nth-order detection method can be applied to any of the heterodyne method and the homodyne method, but the reference grating method has only one incident light beam and is necessarily limited to the homodyne method.

In the above-mentioned interference type alignment method, monochromatic light such as a laser is generally used as the detection light. Due to the monochromaticity, that is, the coherence length is long, a grating mark (position detection mark) is used. Step (depth)
There is a problem in that a large position detection error occurs due to the asymmetry with respect to and the variation in the resist thickness.

Therefore, an interference type alignment method that reduces these influences and enables more accurate position detection is provided (E).
It was proposed by JP-A-6-82215. In the publication (E), a plurality of beams having different wavelengths or a white beam are used, and two diffracted beams obtained by irradiating the beams on a fixed diffraction grating are incident on the first-stage AOM.
By relaying the 0th-order beam, the + 1st-order diffracted beam, and the -1st-order diffracted beam diffracted by this AOM so as to cross each other in the AOM of the second stage, for example, a pair of light-transmitting beams having the first wavelength and a first beam A method is disclosed in which a pair of light-transmitting beams having two wavelengths are formed and the two sets of light-transmitting beams are simultaneously projected onto a lattice mark on a wafer.

At this time, the interference beat light generated from the lattice mark and photoelectrically detected includes a first wavelength component and a second wavelength component, which are added as a light quantity on the light receiving surface of the photoelectric element. Photoelectrically detected in the selected form. Therefore, the mutual phase difference of the interference beat light of each wavelength component due to the influence of thin film interference of the resist layer or the influence of the asymmetry of the mark cross-sectional shape is intensity averaged, and more accurate position detection is possible. It has been done.

[0015]

However, as in the above-mentioned prior art, the illumination light flux used for position detection is made into a beam having a plurality of wavelengths or a predetermined wavelength bandwidth, and a plurality of wavelength components generated from the grating mark are generated. When the same photoelectric element simultaneously receives the interference light including the light, if the illumination light flux contains a high-intensity wavelength component, the diffracted light from the grating mark will also be strengthened at that wavelength component, resulting in an averaging effect. May cause problems. Alternatively, even if the diffracted light is received separately for each wavelength and the position is detected separately, and the average thereof is used as the detection position, the difference in the accuracy in each detection position of each wavelength is not known. The simple average has a disadvantage that the detection accuracy may be deteriorated due to the result of the wavelength having a large detection error.

By the way, generally, a mark (alignment mark) for alignment and position measurement formed on the surface of a wafer or the like is formed with a minute step on the surface.
There is some asymmetry due to a wafer process such as etching or sputtering in a semiconductor processing process or uneven coating of a photoresist layer. The asymmetry causes a decrease in accuracy when detecting the mark position.

Particularly, in the interferometric alignment method in which the mutual interference light of two diffracted lights generated from the grating mark is photoelectrically detected and the photoelectric signal is used, the asymmetry of the grating mark is caused by the asymmetry of the amplitude reflectance of the mark itself. And the position detection accuracy is deteriorated. That is, when the depth (step) of the groove bottom of the line forming the grating mark has a difference in the grating period direction or there is a partial difference in the thickness of the resist layer, the absolute amplitude reflectance of the mark itself is The value and the phase become asymmetric depending on the depth of the groove bottom and the change of the resist thickness.
As a result, the diffracted light generated from the grating mark also has different intensity and phase between the positive order generated in the right direction and the negative order generated in the left direction with respect to the 0th order light, for example. Among them, the difference in intensity hardly deteriorates the position detection accuracy, but the change in phase has a great influence on the position detection accuracy.

Further, the amplitude reflectance and diffraction efficiency of the grating mark greatly vary depending on the step of the mark and the resist thickness. This is because the step difference of the mark changes the phase difference between the light reflected on the upper surface of the mark and the light reflected on the lower surface of the mark, and the multiple interference effect of the resist changes due to the change of the resist thickness. In particular, the problem is that the influence of these changes greatly when the wavelength of the detection light changes.

Also in this point, a method of simultaneously receiving the interference light containing a plurality of wavelength components by the same photoelectric element in the prior art, or simply receiving the diffracted light separately for each wavelength and detecting the positions separately, The method of using the simple average position as the detection position has a disadvantage that accurate position detection cannot always be performed because no consideration is given to how appropriate the detection wavelength is used.

The present invention has been made under such circumstances, and an object thereof is to achieve high averaging effect by maximizing the averaging effect by illuminating a grating mark with an illumination light flux containing a plurality of wavelength components. Another object of the present invention is to provide a new position detection method and device.

[0021]

By the way, the position detection accuracy, such as the variation of the amplitude reflectance and diffraction efficiency of the grating mark due to the variation of the mark step and the resist thickness as described above, the position detection accuracy, is the mark itself under various mark conditions. A simulation can be performed by assuming the amplitude reflectance of

Here, an example of such a simulation result will be described with reference to FIG. This simulation result assumes that a grating mark on a wafer covered with a resist layer is irradiated with a coherent light-transmitting beam having a constant frequency difference from two symmetrical directions, and ± is generated vertically from the grating mark. Mutual interference light of first-order diffracted light,
That is, it is obtained by observing (calculating) the state (amplitude, phase, etc.) of the interference beat light.

The shape of the lattice marks on the wafer assumed in the above simulation is such that the widths of the convex portions and the concave portions are 4 μm and the period P = 8 μm is aligned in the measurement direction.
The cross section of the lattice mark is shown in FIG. 10 (1), and an enlarged view of one period thereof is shown in FIG. 10 (2). The mark step h and the resist thickness d are used as parameters, and the concave portion of the mark has an inclination t = 0. .
It is assumed that there is a taper of 1%. Also, in the concave portion of the mark, the resist surface is dented by 0.3 · h,
The shape of the resist surface was a sine function (period P), and the refractive indexes of the wafer and the resist were 3.5 and 1.66, respectively.
In FIG. 10A, the number of lattice marks is set to 5 for the sake of space, but the actual number of lattice marks is generally larger than that.

In the assumed detection optical system, the wavelength of the detection laser beam is 633 nm (He-Ne laser), and the two beams are symmetrically incident from the ± first order direction with respect to the mark period P. , Which detects the position by receiving a light beam that is reflected / diffracted vertically upward (combined light beam of ± 1st-order diffracted light of both incident lights) (the above-mentioned “± 1st-order detection method” (“± Nth-order detection method N”) =
1)). However, as a detection optical system, a “01th-order detection method” in which two beams are symmetrically incident from the ± 0.5th-order direction with respect to the mark period P, or a “reference grating method” using ± first-order diffracted light is used. However, the result is exactly the same as described above.

In FIGS. 9A and 9B, the horizontal axis represents the resist thickness d [μm] and the vertical axis represents the position detection error [nm].
Is shown. In FIG. 9A, the mark step h is 50, 100,
In case of 150 and 200 nm, the mark step h is shown in Fig. 9 (2).
, The simulation results for 250, 300, 350, and 400 nm are shown, respectively.

Although the detection error varies depending on the change in the resist thickness, it can be seen that when the mark step h is 100 and 300 nm, the variation is small and the absolute accuracy is good.

Since the wavelength of the detection light is 633 nm and the refractive index of the resist is 1.66, the wavelength of the detection light near the mark surface (in the resist) is 381 nm.
0 and 300 nm are approximately equal to 1/4 and 3/4, respectively. Although not shown, the step difference of the wavelength of the detection light in the resist is 5/4 and 7/4 ..., That is, (2m + 1)
As a result of simulation, it was found from the simulation result that the detection error at the mark having a step difference of / 4 times (m is an integer of 0 or more) is extremely small.

If this simulation result is contradictory, the wavelength (wavelength in resist) is 4 of the mark step.
If the detected light flux of / (2m + 1) times is used, the detection error can be made extremely small.

However, there is no conventional method for accurately and easily measuring the level difference of the grating mark used in the interferometric alignment method, and therefore, the level difference of the grating mark to be detected is detected as described above. Of light wavelength (2m
There was no means for easily determining whether or not the condition of +1) / 4 times was met.

Further examination of the above simulation results shows that the detection accuracy is such that the level difference deviates from (2m + 1) / 4 of the wavelength in the resist of the detection light, that is, the level difference is detected instead of the level difference itself. It is estimated that it is greatly affected by the 2/4 of the medium wavelength, that is, the remainder divided (divided) by 1/2.

According to the present invention, in the interferential alignment method using a single wavelength of the illumination light, the step of the mark is the wavelength of the illumination light (more precisely, the wavelength in the resist of the illumination light), (2 m
The present invention is based on the above-described simulation result that the position detection error hardly occurs when it is +1) / 4 times (m is an integer of 0 or more), and the present invention is as follows. Adopt a different method and configuration.

According to a first aspect of the present invention, the period of the lattice mark formed on the substrate on which the fine pattern is formed, has a periodicity (period = P) in a specific direction and repeats concave and convex portions. A position detecting method for detecting a position in a direction, wherein a plurality of pairs of coherent light beams having different wavelengths are incident on the grating mark, and a period of amplitude distribution is 2P / N (N.
Is a natural number) and the periodic direction of which is the same as the periodic direction of the grating mark, and the first step of relatively scanning the interference fringe and the lattice mark in the periodic direction; Of the reflected / diffracted light of the beam, the specularly reflected light of the first light beam and the N of the second light beam
A first combined light beam that is a combined light beam with the second-order diffracted light, and a second combined light beam that is a combined light beam of the specularly reflected light of the second light beam and the Nth-order diffracted light of the first light beam, A second step of separately receiving light for each of the plurality of wavelengths; and for each wavelength based on changes in the light amount signals of the first and second combined light fluxes for each wavelength due to the relative scanning A third step of detecting the position of the grating mark; a step equivalent amount of the grating mark, a change in the light amount signals of the first and second combined light fluxes for each wavelength due to the relative scanning, and the grating mark A fourth step of calculating, for each wavelength, a step difference of the grating mark divided by half of each wavelength of the incident light beam in the medium near the surface of the grating mark, based on the design data of The position of the grating mark detected for each wavelength is The closer the step-equivalent amount calculated for each wavelength is to the quarter-equivalent amount of each wavelength of the incident light beam near the surface of the grating mark, the more weighted the weighted average is, and the weighted average value is calculated. And a fifth step of setting the final detection position of

According to this, in the first to third steps, 0
The same detection as in the interferometric alignment method by the Nth-order detection method is performed, and from the obtained two light amount signals for each wavelength (the light amount signals of the first and second combined luminous fluxes), the grating mark of The position is detected (but for each wavelength).

Further, in the fourth step, the step-corresponding amount of the grating mark is changed based on the change due to the relative scanning of the light amount signals of the first and second combined light beams for each wavelength, and the design data of the grating mark. It is calculated for each wavelength as a remainder obtained by dividing the step of the grating mark by half of each wavelength of the incident light beam in the medium near the surface of the grating mark. This is to detect each wavelength as "a step difference equivalent to a remainder obtained by dividing the step difference by 1/2 of the wavelength in the resist," which becomes clear as a result of the above simulation. The step equivalent amount may be detected in any form of a step as a surplus or a phase amount of light corresponding to this. As a result, whether or not the level difference of the grating mark to be position-detected meets the condition of (2m + 1) / 4 times the in-resist wavelength of the detection light for each wavelength, or the in-resist wavelength of the detection light is detected It is possible to easily determine whether or not the condition of 4 / (2m + 1) times the level difference of the lattice mark to be met is met.

Then, in the fifth step, the step equivalent amount calculated for each wavelength at the position of the grating mark detected for each wavelength is equivalent to ¼ of each wavelength in the vicinity of the grating mark surface of the incident light beam. The closer to the amount, the greater the weight, and the weighted average is calculated, and the weighted average value is used as the final detection position of the lattice mark. That is, the calculated step is the wavelength (in the resist)
A large weight on the detection position at a wavelength close to 1/4 times
A small weight is given to the detection positions at wavelengths apart from 1/4 times, and the position where the detection positions are weighted and averaged is set as the final detection position of the lattice mark. Where 1/4 of each wavelength
Is equivalent to the case of m = 0 of (2m + 1) / 4, but since the step equivalent is a surplus for a half wavelength as described above, there is no need to consider when m> 0. Is 1 of each wavelength near the grating mark surface of the incident light beam
To be close to / 4 equivalent means that the step equivalent is close to (2m + 1) / 4 times each wavelength in the vicinity of the grating mark surface of the incident light beam. Therefore, the final detection position of the lattice mark in the fifth step is 4 / (2m +
1) It is a weighted average value that emphasizes the detection result with the detection light of the wavelength that is the closest to double, and it is much higher than the case of simply averaging the mark detection positions for each wavelength even for an asymmetric grating mark. It is possible to perform highly accurate position detection and maximize the averaging effect.

In this case, in the first step, a plurality of pairs of coherent light beams having different wavelengths are time-divisionally incident on the grating mark for each wavelength, and the period of the amplitude distribution is 2.
Interference fringes of P / N (N is a natural number) whose periodic direction is equal to the periodic direction of the grating mark are formed for each wavelength, and
The interference fringes for each wavelength and the grating mark may be relatively scanned in the periodic direction. When a plurality of pairs of coherent light beams having different wavelengths are incident on each wavelength in a time-divisional manner, the light receiving means for reflected / diffracted light and the configuration of the signal processing system are simplified.

In these cases, the position of the grating mark for each wavelength is detected by the first combined light beam and the second light beam accompanying the relative scanning.
It is desirable to average the detection positions obtained based on the respective phases of the changes in the respective light amount signals of the combined light flux.

Further, the step equivalent amount is calculated by calculating the ratio of the widths of the concave portion and the convex portion of the lattice mark, the phase difference between the light amount signal changes of the first combined light beam and the second combined light beam due to relative scanning, and It can be performed based on the contrast. Alternatively, when the light quantity ratio between the 0th-order diffracted light reflected and diffracted by the grating mark and the Nth-order diffracted light is measured for each wavelength of the incident light beam, the step equivalent amount is calculated by using the concave and convex portions of the grating mark. The ratio of each width, the first combined luminous flux and the second
Can be performed based on the phase difference of each light amount signal change of the combined light flux and the measured light amount ratio. In this case, 0
Since the light quantity ratio between the second-order diffracted light and the N-th order diffracted light is directly measured, the step equivalent amount can be calculated with higher accuracy than in the case where the light quantity ratio is calculated based on the contrast.

According to a sixth aspect of the present invention, the periodic direction of the lattice mark in which the concave portion and the convex portion are repeated with periodicity (period = P) in a specific direction formed on the substrate on which the fine pattern is formed A position detecting device for detecting the position of the lattice mark, wherein an interference fringe having a period of amplitude distribution of 2P / N (N is a natural number) and a period direction of which is equal to the period direction of the lattice mark is formed on the lattice mark. A light-transmitting optical system for injecting a plurality of pairs of coherent light beams having different wavelengths; a specular reflection light of a first light beam and a second light of the reflected / diffracted light of the incident light beam by the grating mark; A first combined light beam that is a combined light beam of the N.sup.th-order diffracted light of the first light beam, and a second combined light beam of the regularly reflected light of the second light beam and the N.sup.th-order diffracted light of the first light beam. Separate the combined luminous flux and each of the multiple wavelengths. A light receiving means for photoelectrically converting into light; a relative scanning means for relatively scanning the grating mark and the interference fringes in the periodic direction; a combination of the first and second combined light fluxes obtained by the light receiving means for each wavelength. Position detecting means for detecting the position of the grating mark for each wavelength based on a change in the light amount signal due to the relative scanning; and a step equivalent amount of the grating mark for the first wavelength for each wavelength obtained from the light receiving means. , The wavelength of the incident light beam in the medium near the surface of the grating mark based on the change in the light amount signal of the second combined light flux due to the relative scanning and the design data of the grating mark. Step difference detecting means for calculating each wavelength as a remainder divided by half; the position of the grating mark detected for each wavelength, the step equivalent amount calculated for each wavelength is the incident light beam. of Serial weighted average with a greater weight closer to 1/4 equivalent amount of each wavelength at the grating mark near the surface, and a calculating means for the average value as the final detected position of the grating mark.

According to this, in order to form an interference fringe having a period of amplitude distribution of 2P / N (N is a natural number) on the grating mark by the light transmitting optical system, and the period direction thereof is equal to the period direction of the grating mark. A plurality of pairs of coherent light beams having different wavelengths are made incident, and the relative scanning means relatively scans the interference fringes and the grating mark in the periodic direction.

Next, in the light receiving means, of the reflected / diffracted light of the incident light beam by the grating mark, it is the combined light flux of the specularly reflected light of the first light beam and the Nth-order diffracted light of the second light beam. The first combined light flux, the second combined light flux that is the combined light flux of the specularly reflected light of the second light beam and the Nth-order diffracted light of the first light beam are separately and separately for each of a plurality of wavelengths. It is photoelectrically converted. The position detecting means detects the position of the grating mark for each wavelength from the change of the light amount signals of the first and second combined light fluxes for each wavelength obtained by the light receiving means due to the relative scanning, and the step detecting means. Then, the step-corresponding amount of the grating mark is determined based on the change in the light amount signals of the first and second combined light fluxes for each wavelength obtained by the light receiving means due to the relative scanning and the design data of the grating mark. It is calculated for each wavelength as a remainder obtained by dividing the step by half of each wavelength of the incident light beam in the medium near the surface of the grating mark.

In the calculating means, the position of the grating mark detected for each wavelength is calculated for each wavelength, and the step equivalent amount is 1 for each wavelength in the vicinity of the grating mark surface of the incident light beam.
/ 4 weighted and weighted average
The average value is used as the final detection position of the lattice mark.

Therefore, similar to the invention described in claim 1,
A final weighted average value can be used as the final detection position of the grating mark, with a weighted average value that emphasizes the detection result with the detection light having the wavelength closest to 4 / (2m + 1) times the step, and even for asymmetrical grating marks. As compared with the case of simply averaging the mark detection positions for each wavelength, it is possible to perform extremely highly accurate position detection and maximize the averaging effect.

Here, the position detecting means calculates the average value of the detection positions obtained on the basis of the respective phases of the respective light quantity signal changes of the first combined light beam and the second combined light beam due to the relative scanning, and the average position of the lattice mark. You may make it detect as.

Further, the step detecting means determines the ratio of the widths of the concave portion and the convex portion of the lattice mark, the phase difference and the contrast of the respective light amount signal changes of the first combined light beam and the second combined light beam due to the relative scanning. Alternatively, the step equivalent amount may be calculated based on. Alternatively, when a light quantity ratio measuring means for measuring the light quantity ratio of the 0th-order diffracted light reflected and diffracted by the grating mark and the Nth-order diffracted light for each wavelength of the incident light beam is further provided, the step detecting means is a grating mark. The ratio of each width of the concave portion of the
The step equivalent amount may be calculated based on the phase difference between the changes in the respective light amount signals of the first combined light beam and the second combined light beam due to the relative scanning, and the light amount ratio obtained by the light amount ratio measuring means. . In the latter case, since the light quantity ratio between the 0th-order diffracted light and the Nth-order diffracted light is directly measured, the step equivalent amount can be calculated with higher accuracy than in the former case in which the light quantity ratio is calculated based on the contrast. It can be calculated.

The relative scanning means may be constituted by a stage capable of scanning the substrate in the periodic direction of the grating mark, but the first of the plural pairs of coherent light beams having different wavelengths. The frequency of the light beam may be slightly different from the frequency of the second light beam, and the interference fringes formed thereby may be moved on the grating mark in the periodic direction at a constant speed. According to the latter, it is possible to detect even if the substrate remains stopped during the detection.

[0047]

【Example】

<< First Embodiment >> A first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a position detecting device 1 according to the first embodiment.
The structure of the main part of 00 is shown schematically. The position detecting device 100 includes a wafer stage WST on which a wafer W as a substrate is mounted, a drive system 21 for driving the wafer stage WST in a two-dimensional direction, and a light transmitting optical system 102.
And a light receiving optical system 104.

Of these, the light-transmitting optical system 102 includes three laser light sources LS1, LS2, LS3, a mirror 1, a dichroic mirror 2, 3, a mirror 4, and a rotary radial grating plate RR.
G, a collimator lens 5, a light flux selecting member 6, adjusting optical systems 7, 8 and 9 made of parallel plate glass, a beam splitter (half mirror) 10, an objective lens 11 and the like. Here, the operation of the light transmitting optical system 102 will be described together with the operation of each of the above components.

The three laser light sources LS1, LS2, L
S3 emits laser beams LB1, LB2 and LB3 having different wavelengths .lambda.1, .lambda.2 and .lambda.3, respectively. In this embodiment, for example, the laser light source LS1 is a He--Ne laser light source of .lambda.1 = 633 nm, and the light source LS2 is .lambda.2 = 690n.
.lamda.3 = 780n as a semiconductor laser light source of m and light source LS3
It is assumed that m semiconductor laser light sources are used, and therefore the wavelength relationship is set to λ1 <λ2 <λ3.

These three beams LB1, LB2, LB
3 is combined into one coaxial beam LB0 via the mirror 1 and the dichroic mirrors 2 and 3, and is reflected by the mirror 4 to enter the rotating radial grating plate RRG. The grating plate RRG rotates at high speed around the rotation axis C0 at a constant angular velocity in one direction, and functions to increase or decrease the frequency of the diffracted light of each order diffracted by the grating plate RRG by an amount corresponding to the angular velocity. Have.

FIG. 2 shows this rotating radial grating plate RRG.
An enlarged perspective view of is shown. The rotating radial grating plate RRG is made of a disk-shaped member, and transmission phase diffraction gratings RG are formed on the grating plate RRG at predetermined pitch intervals along the circumferential direction over 360 degrees. here,
It is assumed that the rotation axis C0 of the lattice plate RRG is set parallel to the X axis of the XYZ coordinate system. When the beam LB0 is vertically incident on the grating RG of the grating plate RRG, various diffracted lights are generated in addition to the 0th order light D0, but in the first embodiment, ± 1.
Since the heterodyne system is realized by using the diffracted light of the order, only the ± 1st diffracted light from the grating plate RRG is shown in FIGS. 1 and 2.

Now, when the beam LB0 is vertically incident on the grating RG of the grating plate RRG, as shown in FIG. 2, from the grating RG of the grating plate RRG, the first-order diffracted beam ± 1 made from the beam LB1 of the wavelength λ1. D11 and beam L of wavelength λ2
First-order diffracted beam ± D12 made from B2 and first-order diffracted beam ± D13 made from beam LB3 of wavelength λ3
Occurs. The diffraction angle θ of the first-order diffracted beam for each wavelength is expressed as follows.

[0054]

## EQU1 ## sin θn = λn / Prg (1) where the subscript n represents the distinction of each wavelength (n = 1, 2,
3), Prg represents the period of the lattice RG.

On the other hand, the first-order diffracted beam generated from the grating plate RRG receives a constant frequency shift Δf regardless of the wavelength. That is, the grating RG of the grating plate RRG is the beam LB0.
If the velocity across V is V, then Δf = V / Prg,
The frequency of the + 1st order diffracted beam is Δ from the frequency of the 0th order light D0.
The frequency of the -1st-order diffracted beam increases by f and the 0th-order light D
It is lower than the frequency of 0 by Δf. Thus, the rotary radial grating plate RRG functions as a kind of frequency shifter.

The + 1st-order diffracted beam + D1n (n = 1, 2,
3) Transmitted beam + LF and -1st-order diffracted beam-
A light-transmitting beam -LF composed of D1n (n = 1, 2, 3),
As shown in FIG. 1, the 0th-order light D0 is converted by the collimator lens 5 so that the principal rays are parallel to each other, and reaches the light flux selecting member 6. This luminous flux selection member 6 is
It functions as a so-called spatial filter placed on the so-called Fourier transform plane, where the 0th-order light D0 is blocked and the 1st-order diffracted light ±
The light transmission beam ± LF by D1n passes.

After that, the transmitted light beams ± LF reach the beam splitter (half mirror) 10 through the adjusting optical systems 7, 8 and 9 which are made of parallel plate glass whose tilt amount is variable.

The adjusting optical system 7 has a function of decentering the optical axis of the lens 5 without changing the distance between the light transmitting beam + LF and the light transmitting beam -LF in the Fourier space. 9 is a light-sending beam + LF and a light-sending beam -LF
It has a function of individually adjusting the positions of the optical axis and the optical axis. That is, the adjusting optical system 7 adjusts the inclination of the light-transmitting beam (± LF) with respect to the wafer W in the radiation direction centered on the optical axis of the objective lens 11, and the adjusting optical systems 8 and 9 adjust the objective lens on the wafer W. The opening angles of the light-sending beams + LF and -LF with respect to the optical axis 11 are adjusted.

The transmitted beam ± LF is split into two by the beam splitter 10, and one (reflected light) is the objective lens 1
1, and becomes a parallel light flux, and is incident on the wafer W at different angles for each wavelength.

Here, on the wafer W, a lattice mark (position detection mark) having a sectional shape as shown in FIG.
MG is formed in advance, and in FIG. 1, this lattice mark (position detection mark) MG is located exactly at the incident position of the light transmitting beam ± LF.

Therefore, on the grating mark MG, the interference fringes formed by the interference of the light-transmitting beams ± D11 of the wavelength λ1, the interference fringes formed by the interference of the light-transmitting beams ± D12 of the wavelength λ2, and the wavelength λ3. Three of the interference fringes created by the light transmission beams ± D13 appear in the same period and the same phase. Further, due to the frequency difference 2 · Δf between the light-transmitting beams + LF and −LF, the interference fringes appear to move on the grating mark MG in one direction (periodic direction of the grating mark MG) at a constant speed. To be observed. The moving speed thereof is proportional to the speed V of the grid RG of the rotating radial grid plate RRG. As is apparent from this, in the first embodiment, the relative scanning means is constituted by the rotating radial grating plate RRG.

As is clear from FIG. 1, the wafer W
The surface (lattice mark MG) and the radial lattice plate RRG are
The collimator lens 5 and the objective lens 11 are arranged so as to be conjugated (imaging relationship) with each other by a combined system. Therefore, the diffraction image of the ± 1st-order diffracted light of the grating RG of the radial grating plate RRG is formed on the grating mark MG of the wafer W, but since the 0th-order light D0 is shielded, it is half the period of the grating RG. A bright-dark image (interference fringe intensity distribution) is formed.

In this embodiment, the period Pif of the amplitude of the interference fringes on the wafer W (twice the period of the intensity distribution) is set to 2 / N times (N is a natural number) the period Pmg of the lattice mark MG. To do. At this time, for any of the above three wavelengths, the grating mark M of one (first) incident beam (for example, + LF)
0th-order diffracted light (regular reflection light) by G and the other (second)
N by the grating mark MG of the incident beam (for example, -LF)
The second-order diffracted light is a first combined light beam which is generated in the same direction and interferes with each other, and the grating mark M of the second incident beam.
The 0th-order diffracted light by G and the Nth-order diffracted light by the grating mark MG of the first incident beam are also generated in the same direction and become a second combined light flux that interferes with each other. And the first of these,
The second combined light flux is beat light whose intensity is modulated at a frequency of 2 · Δf according to the frequency difference between the incident beams ± LF that are light sources.

As described above, in order to generate the 0th-order diffracted light and the Nth-order diffracted light in the same direction, from a different point of view, the focal length of the objective lens 11 is F0 and the transmitted light beam for each wavelength is The distance DLn on the Fourier transform plane of ± LF (near the beam splitter) is determined with respect to the detection direction of the grating mark MG.

[Formula 2] DLn = ± NF0λn / Pmg (2) The setting of the interval DLn for each wavelength can be adjusted by appropriately determining the period of the grating RG of the rotating radial grating plate RRG and the focal length of the collimator lens 5.

Further, even if the grating mark MG is slightly defocused (shifted in the direction of the optical axis AX), the light-sending beam ± LF is equal to the grating mark MG (wafer W) so that an error does not occur in the detection position. It is preferable that the light beams are incident at an inclination angle, that is, the light beams pass through positions on the Fourier transform plane, which are separated from each other by DLn / 2 in the detection direction of the grating mark MG from the optical axis AX.

That is, the position detecting device 1 according to the first embodiment.
The configuration of 00 is close to the configuration of the conventional “0th order method”.

By the way, if there is a slight chromatic aberration in the optical systems 5, 11, etc., the interference fringes formed on the wafer W will have a positional shift (phase shift) and a periodic shift for each color. There is a fear. Therefore, the adjustment optical systems 7, 8 and 9 in FIG. 1 are used to correct such a shift. These optical systems 7, 8 and 9 are made of parallel plate glass, and if a material having a large chromatic dispersion is used as the material thereof, the positional displacement and phase of the interference fringes formed on the wafer W for each wavelength component are mutually different. The shift can be minutely changed. Alternatively, as the adjusting optical systems 7, 8 and 9, a parallel flat plate glass having a small chromatic dispersion and a parallel flat plate glass having a large chromatic dispersion are combined, and the inclination fringes of the parallel flat plate glass having a large chromatic dispersion are adjusted so that the interference fringes of each wavelength component are mutually The overall tilt error of the light-transmitting beams ± LF on the wafer W caused by the correction can be corrected by adjusting the tilt of the parallel plate glass having a small chromatic dispersion.

Next, the light receiving optical system 104 will be described. The light receiving optical system 104 includes the objective lens 11,
Dichroic mirrors 16 and 18, wavelength selection filter 1
2, condenser lens (Fourier transform lens) 13, reference grating SG, spatial filter 14, photoelectric converters (detectors) 17a, 17b, 19a, 19b, 20 as light receiving means.
a, 20b and a detector 15 for generating a reference signal. Here, the light receiving optical system 104 will be described together with the operation of each of the above components.

The first and second combined light fluxes generated from the grating mark MG illuminated by the interference fringes as described above are
It passes through the objective lens 11 and the beam splitter 10 and reaches the dichroic mirror 16. The beams A1 and B1 of the component of wavelength λ1 of the first and second combined light fluxes are reflected by the dichroic mirror 16 and are incident on photoelectric converters (detectors) 17a and 17b, respectively, and the light quantity signals thereof are electric signals IA1. , IB1.

Of the first and second combined light fluxes, the wavelengths λ2 and λ
The beam of 3 passes through the dichroic mirror 16 and reaches the dichroic mirror 18. Then, of the first and second combined luminous fluxes A and B, the beams A2 and B of the component of wavelength .lambda.2 are obtained.
2 is reflected by the dichroic mirror 18, enters the detectors 19a and 19b, respectively, and is photoelectrically converted. On the other hand, the beams A3 and B3 of the wavelength .lambda.3 are transmitted through the dichroic mirror 18 and are respectively detected by the detector 2
It is incident on 0a and 20b and is photoelectrically converted. Since the wavelength division by the dichroic mirrors 16 and 18 may be insufficient depending on the intervals of the wavelengths λ 1, λ 2 and λ 3 used, an interference filter (narrow bandpass filter) should be placed immediately before each detector. Good.

Each detector 17a, 17b, 18a, 1
Photoelectric signals IA1, IB1, by 8b, 19a, 19b,
Each of IA2, IB2, IA3, and IB3 becomes a sine wave having the same frequency as the beat frequency 2.multidot..DELTA.f while the interference fringe irradiates the grating mark MG portion.

On the other hand, the light beam (transmitted beam ± LF) transmitted from the collimator lens 5 through the beam splitter 10.
Is the primary beam of a specific wavelength in the transmitted light beam ± LF, which is the primary beam ± D12 of λ2, and is incident on the condenser lens (Fourier transform lens) 13 via the wavelength selection filter 12. . Then, irradiation is performed by superimposing it on the transmissive reference grating SG. Here again, the reference grating SG is arranged conjugate with the rotary radial grating plate RRG with respect to the combined system of the collimator lens 5 and the condenser lens 13. Therefore, one-dimensional interference fringes due to the two-beam interference of the primary beams ± D12 are also formed on the reference grating SG, which has a beat frequency of 2
・ Move at a speed corresponding to Δf.

Therefore, if the period of the reference grating SG and the period of its interference fringes are appropriately determined, the ± 1st-order diffracted light generated from the reference grating SG travels in the same direction as an interference beam Bms, which passes through the spatial filter 14. Transmitted through detector 15
Received. The photoelectric signal Ims of this detector 15 is also
The sine wave has the same frequency as the beat frequency 2 · Δf, and its signal Ims becomes the reference signal of the heterodyne system.

In the first embodiment, the light flux to be applied to the reference grating SG is one wavelength out of the above three wavelengths, but this is for the following reason. That is, the reference lattice SG
Is formed by depositing a chrome layer on a glass plate and etching the chrome layer so that transparent lines and light-shielding lines are alternately formed.
It is made as an almost ideal grating (a grating whose amplitude transmittance is symmetric) having no asymmetry like the above grating mark MG and the problem of the resist layer. Therefore, a sufficient accuracy can be obtained even if only a primary beam corresponding to any one of the three wavelengths λ1, λ2 and λ3 is used as the pair of light-transmitting beams with which the reference grating SG is irradiated.

Of course, 3 included in the transmitted light beams ± LF
All the primary beams ± D11, ± D12, ± D13 are simultaneously applied to the reference grating SG, and the grating marks MG on the wafer W are irradiated.
Similarly to the above, multicolor interference fringes may be formed. However, in this case, the interference fringes formed by the three wavelengths are also
An adjustment mechanism for matching the position and the cycle is provided, or the interference beam Bms after passing through the reference grating SG is transferred to the wafer W.
Similar to the detection of the above mark, it is necessary to perform it separately for each wavelength.

Next, wafer stage WST will be described. The wafer stage WST is two-dimensionally driven by a drive system 21 including a drive motor in a plane (XY plane) perpendicular to the optical axis AX of the objective lens 11. This driving method may be either a method of rotating the feed screw by a motor or a method of directly moving the stage main body by a linear motor. The wafer W is suction-held on the wafer stage WST via a wafer holder (not shown). This wafer stage WST
The moving position (coordinate position) of is sequentially measured by the laser interferometer 22. The measurement value of the laser interferometer 22 is used for feedback control of the drive system 21.

Further, a fiducial mark (reference mark) plate FP is provided on a part of wafer stage WST. On this mark plate FP, a reference mark FG (a period is a lattice mark MG on a wafer is formed by patterning lines and spaces with a chrome layer on the surface of quartz glass.
The same) is formed. In the actual position detection, prior to the position detection of the lattice mark MG on the wafer W, the position of the reference mark FG is detected to correct various device-dependent errors, which will be described in detail later.

In the device of the first embodiment, a semiconductor laser is used as the light source. In this case, the semiconductor laser (LS2,
LS3) and a mirror 1 and a dichroic mirror 2 are provided with a shaping optical system for removing astigmatism (a plurality of tilted parallel flat glass plates, etc.) and each wavelength component of the beam LB0 combined into one. It is preferable that the luminous flux components for each of them have substantially the same diameter. Also, when a light source other than a semiconductor laser is used as the light source, it is desirable to provide a beam shaping optical system for making the diameters of the combined beam LB0 uniform for each wavelength component.

FIG. 3 shows an example of the position detection circuit which constitutes the position detection device 100. This position detection circuit has three wavelengths corresponding to wavelengths λn (n = 1, 2, 3).
One phase difference detection circuit SAn (n = 1, 2, 3) and three detection position correction circuits CAn (n = 1, 2, 3) respectively provided corresponding to these phase difference detection circuits SAn.
And an averaging circuit SS. Here, the role of each circuit forming the position detection circuit will be briefly described.

In the case of the heterodyne system as in the first embodiment, as described above, when the above-mentioned interference fringe irradiates the grating mark MG portion or the reference mark FG, each photoelectric signal IA1, IB1, IA2, IB2, Each of IA3, IB3 and Ims is a sine wave having the same frequency as the beat frequency 2 · Δf. An example of these signals is shown in FIGS.

Of these, FIG. 4A shows the detector 17a.
Which is the output of the first combined beam of light having wavelength λ1 of A1
The light amount signal IA1 of the detector 17 is shown in FIG.
The light quantity signal IB1 which is the output of b is shown. Further, FIG. 3C shows the reference signal Ims which is the output of the detector 15. Between these signals, with reference to the reference signal Ims,
There is a phase difference of ΔA1 and ΔB1. The amount of these phase differences corresponds to the position of the lattice mark MG and the amount of step difference.

Similarly, FIGS. 5 (1), 5 (2) and 5 (3) respectively show the light amount signals IA2 and IB2 of the wavelength λ2 and the reference signal Ims.
FIG. 6 (1), (2),
(3) shows the light quantity signals IA3, IB3 and the reference signal Ims (same as in FIG. 4 (3)) of the wavelength λ3, respectively, and the phase difference quantity in these figures also corresponds to the position and the step amount of the grating mark MG. It has become a thing.

In the position detecting circuit of FIG. 3, the phase difference detecting circuits SA1, SA2 and SA3 first detect the phase difference between them. That is, each phase difference detection circuit SAn
In (n = 1, 2, 3), each input signal IAn, IBn
Of the phase difference (ΔAn, ΔBn [ra
d]) is detected. To convert this phase difference into the position of the grating mark MG, N.times.Pmg / (2π) times (N is the period Pmg of the grating mark MG and the period of the amplitude of the interference fringes formed on the grating mark MG as described above. However, in the “0N-order method”, the average value of the detection positions obtained from these two phase differences is the grating mark MG for each wavelength, as described in the description of the prior art. Since each of the phase difference detection circuits SAn has the average value ΔXn,

## EQU3 ## ΔXn = {ΔAnNPmg / (2π) + ΔBnNPmg / (2π)} / 2 (3) is output.

Further, each phase difference detection circuit SAn is configured to detect the step difference of the lattice mark MG based on the respective input signals IAn, IBn and the respective widths a, b of the concave portion and the convex portion of the lattice mark MG input from a console (not shown) or the like. The considerable amount δn is calculated as a phase amount of light which is a surplus obtained by dividing the true step difference by half λrn / 2 of the wavelength λrn in the vicinity of the surface of the grating mark MG of the detected light flux of wavelength λn. Wavelength λrn near the surface of the grating mark MG
Means, for example, that the lattice mark MG is a resist or a glass (P
SG) or the like, it means the wavelength in the transparent substance (medium), and when the surface of the lattice mark is exposed, the wavelength in air, that is, λn Means itself. Further, the algorithm for calculating the step equivalent amount Δn is a feature of the present invention (the present embodiment), and its details will be described later.

By the way, the above-mentioned detected position ΔXn is the amount of positional deviation (phase deviation) with respect to the reference signal Ims, and is not the position of the lattice mark MG itself on the wafer W. Therefore, a position reference is required on the wafer W or the wafer stage WST in order to correspond the above-mentioned positional deviation amount obtained from the reference signal Ims to the position on the wafer W.

The above-mentioned reference mark FG is a mark which serves as this position reference. Prior to detecting the position of the lattice mark MG on the wafer W, the position of the reference mark FG is first detected and the above-mentioned position obtained from the reference signal Ims. The relationship between the shift amount and the position on wafer stage WST is obtained (baseline check). Specifically, first, while monitoring the output of the laser interferometer 22, the drive system 21 moves the wafer stage WST so that the reference mark FG is located at the position detection beam ± LF irradiation position. Then, the position detection as described above is performed on the reference mark FG, and the reference signal I
The position ΔFXn of the reference mark FG with respect to ms is obtained. Each detection position correction circuit CAn detects the detection position Δ for each wavelength.
FXn and the output LFG of the laser interferometer 22 at this time are stored in a memory (not shown). In this case, if the optical system is adjusted so that the positions of the interference fringes at the respective wavelengths are perfectly aligned on the wafer W (and the reference mark FG), then Δ
FXn becomes equal at each wavelength λn.

Next, the wafer stage WST is moved to detect the position of the lattice mark MG on the wafer W. Each detection position correction circuit CAn outputs the output LMG of the laser interferometer 22 at that stage position and A value Δ obtained by adding the detection result ΔXn for each wavelength to the difference in the output LFG at the reference mark FG detection position stored in the memory and further subtracting ΔFXn above.
Let Xn ′ be the detection position at each wavelength λn.

The averaging circuit SS calculates the final detection position ΔX of the lattice mark MG based on the detection position ΔXn 'and the step equivalent amount δn obtained as described above. Specifically, based on the above-described principle that "the detection error is extremely small when the mark step is (2m + 1) / 4 times the wavelength in the resist of the detected light flux, the step difference amount δn corresponding to each wavelength λn".
Π / 2 [rad] (corresponding to 1/4 of the wavelength λn of the detected light beam (m = 0: the step equivalent δn is a half-wavelength remainder, m>
If 0 is not considered), a large weight is added to the detected position ΔXn ′, and if it is far away, a small weight is applied to perform weighted averaging. As a result, the final grid mark MG
The detection position ΔX of is heavily weighted by the detection result of the detection light having a wavelength close to 4 / (2m + 1) times the step,
In addition, since the averaging effect is obtained by increasing the number of wavelengths, the accuracy is higher than that of the conventional method.

As an example of the weight Wn, for example,

## EQU00004 ## Wn = cos [(. Delta.n-.pi./2)]...(4) and

## EQU5 ## Wn = [1 + cos {2 (δn-π / 2)}] / 2 (5) is used. And

[Mathematical formula-see original document] The weighted average may be obtained by ΔX = (ΣWn.ΔXn ') / ΣWn (6) Also, the weight Wn
Other than the above, any value may be used as long as δn is large in the vicinity of π / 2 and becomes smaller as the distance from π / 2 becomes smaller.

Next, the features of the present invention (this embodiment),
The principle and method of detecting the level difference of the lattice mark MG will be described.

FIG. 7 shows an example of the lattice mark MG in an enlarged manner, where it is assumed that the width of the concave portion is a, the width of the convex portion is b, and the step between both portions is h. Note that, in FIG. 7 and the following description, for simplification, it is assumed that no resist is applied on the lattice mark MG, that is, λrn = λn. Further, the amplitude reflectances for the detection light of the wavelengths λ (where λ is any of the above λn (n = 1, 2, 3)) of the concave portion and the convex portion are φa and φb. At this time, the amplitude reflectances φa and φb represent the amplitudes of the reflected light within the plane at the same position in the depth direction (vertical direction in FIG. 7). More specifically, assuming that this reference surface is the surface of the convex portion of the lattice mark MG, for example, φa is a factor corresponding to the amplitude reflectance on the concave surface and the round-trip optical path difference (phase difference) of the step h, That is, it is multiplied by exp (4πih / λ). The same applies to φb, but since the surface of the convex portion of the mark MG is considered as the reference surface here, the factor of the optical path difference (= 0) is exp (4πi0 / λ) = 1.
Therefore, if the phase difference between φa and φb is obtained, the step amount h can be obtained.

Generally, the amplitude distribution of the diffracted light generated from each of the concave portion and the convex portion in FIG.
It is represented as an nc function. For example, the amplitude distribution of the diffracted light generated from the concave portion having the width a is as follows with respect to the periodic direction of the step pattern of FIG.

## EQU00007 ## .phi.A (u) =. Phi.a.sin (.pi.au) / (. Pi.u) ... (7). Where u is the diffraction angle Θ

## EQU00008 ## u = sin .THETA ./. Lambda.n (8), and similarly, the amplitude distribution of the diffracted light generated from the convex portion with the width b is

## EQU00009 ## .phi.B (u) =. Phi.b.sin (.pi.bu) / (. Pi.u) (9). At u = 0 (zero-order diffracted light), these are a · φa and b · φb, respectively.

The amplitude distribution of the diffracted light from the pattern in which the concave portions and the convex portions are periodically arranged at the pitch P as shown in FIG.

## EQU10 ## ψ (u) = {ψA (u) + ψB (u) · exp (πiPu)} × Pir (u) ...... (10) Pir (u) = sin (lπPu) / sin (πPu) ...... (11) (l is the number of repetitions of the periodic lattice mark MG (integer))
Becomes In the derivation of the equation (10), the center of the concave portion was used as the reference of the phase of the diffracted light, but of course the center of the convex portion may be used as the reference.

The above Pir (u) is called the "periodic term" of the diffraction grating, and if the repetition number l of the grating mark MG is large, it corresponds to the j-th order diffracted light, u = j / P.
(J is an integer) has a non-zero value l, and is almost 0 otherwise. In the present invention, only the 0th-order diffracted light and the Nth-order diffracted light from the grating mark MG are used.
(U) may be a constant value (l). Also, in equation (10)
exp (πiPu) becomes 1 in the 0th-order diffracted light (u = 0) and becomes (−1) ^N in the ± Nth-order diffracted light (u = ± N / P). From this, the 0th and Nth order diffracted lights generated from the grating mark MG as shown in FIG.
Are

[Equation 11] ψ 0 = a · φa + b · φb ………… (12) ψN = a ′ · φa + (− 1) ^N · b ′ · φb ………… (13) a ′ = P · sin (Nπa / P) / π ... (14) b ′ = P · sin (Nπb / P) / π (15)

FIG. 8 shows the process in which the diffracted light amplitudes ψ 0 and ψ N are derived from the amplitude reflectances φa and φb as described above in polar coordinates of complex numbers. In addition, in FIG.
Although φa is a real number (on the Real axis) for simplification,
If the phase difference between φa and φb (4πh / λ = ω) is invariant, the result derived even if φa is a complex number does not change. Further, in FIG. 8, only the case of N = 1 is illustrated for simplification, but the following discussion is similarly applicable to N of 2 or more.

FIG. 8A shows that the 0th-order diffracted light amplitude ψ 0 is determined from the amplitude reflectances φa and φb.
(2) indicates that the first-order diffracted light amplitude ψ1 is determined from the amplitude reflectances φa and φb. As mentioned above, amplitude reflectance φ
The phase difference between a and the amplitude reflectance φb is ω. FIG. 8 (3) shows the ψ obtained from (1) and (2) in FIG.
0, ψ1 are represented on the same polar coordinate, and the phase difference Δ between ψ0 and ψ1 (the phase difference between the 0th-order diffracted light and the 1st-order diffracted light) Δ in the figure is the combined luminous flux An, Bn of FIGS. "Phase difference" between the light intensity signals IAn and IBn (i.e., .DELTA.Bn-.DELTA.
An) equal to half the amount. That is, the light quantity signal IAn
, IBn can be measured. Of course, this is not limited to the case of N = 1, but any N (ψ
N) correct.

Further, the ratio of the magnitudes of ψN and ψ0 (| ψN
│: │ψ 0 │), the light quantity signal I
It is possible to measure from An and IBn. Both signals I
The maximum values AMAXn and BMAXn of An and IBn are the intensities in the state where ψ0 and ψN are amplitude-added in the same phase, and the minimum value A
MINn and BMINn are intensities in the case where ψ 0 and ψ N are amplitude-added in opposite phases,

## EQU12 ## AMAXn≈BMAXn≈ (| ψ0 | + | ψN |) ² (16) AMINn≈BMINn≈ (| ψ0 |-| ψN |) ² (17) The contrast γ of both signals is

[Mathematical formula-see original document] γ = (AMAXn-AMINn) / (AMAXn + AMINn) = 2 · | ψ0 ｜ ・ ｜ ψN ｜ / (│ψ0 │ ² + ｜ ψN │ ² ) ... (18) Therefore, the contrast γ is measured. Then, from equation (18),

[Equation 14] | ψN | = β · | ψ0 | ... (19) β = {1 ± √ (1-γ ² )} / γ (20) and the ratio β is obtained. Although ± in the formula (20) cannot be uniquely determined, since the intensity of the Nth-order diffracted light is generally weaker than that of the 0th-order diffracted light, − (minus) is used. And this gives ψ N

[Expression 15] ψN = β · ψ0 · exp (iΔ) It becomes possible to express as (21).

When the above Δ and β are obtained, the above process of deriving the diffracted light amplitude from the amplitude reflectance is followed in reverse, and from the diffracted light amplitudes ψ 0 and ψ N, the amplitude reflectances φa and φb of the periodic step pattern are obtained. Can be asked. Specifically, the simultaneous equations of equations (12) and (13) may be solved based on the known parameters.

Generally, in the processing of a semiconductor integrated circuit, the controllability of the pattern line width is excellent. Therefore, the widths a and b of the concave and convex portions of the lattice mark MG are almost as designed, that is, they are known. Then, the width a of the concave portion and the convex portion,
Similarly, a ′ and b ′ calculated from b are also known. Therefore, in the simultaneous equations of equations (12) and (13), only unknown variables (variables that have not been measured) are φa and φb, and therefore the simultaneous equations can be solved for φa and φb. as a result,

Equation 16] φa = {b '· ψ0 - (- 1) N · b · ψN} / C ......... (22) φb = (a' · ψ0 -a · ψN) / C ......... (23) (C = a * b '-(-1) ^N * a' * b) is obtained. (ΨN
Equation (21) is substituted into. ) In equations (22) and (23), the phase of ψ 0 is not known, but
Since the final result is that the phase difference (= ω) between φa and φb is known, the phase of φ0 (angle formed with the Real axis) may be any value.

From the above, from equations (22) and (23), φa
, Φb value (complex number) is obtained. Then, the respective phases (ωa, ωb) of both are obtained from the real and imaginary parts of φa and φb. That is,

Ωa = tan ^-1 {Im (φa) / Re (φa)} ……… (24) ωb = tan ⁻¹ {Im (φb) / Re (φb)} ……… (25) . Then, if the difference between them is ωb−ωa = ω, then φa
, Φb phase difference ω is obtained. The phase difference ω can take a value up to 4π [rad] as an absolute value, but due to the periodicity of the trigonometric function (tan ^-1 ), when the value of ω exceeds 2π, ω-2π is ω. , Ω is negative, then ω
Let ω be 2π added until becomes positive.

This phase difference ω corresponds to the round-trip optical path difference (phase difference) of the step h as described above,

[Equation 18] ω = 4πh / λ, that is, h = ω · λ / (4π) ... (26) The final step h can be obtained from the relationship. However, the step h here is in the range of 0 to λ / 2 according to the above method of determining ω. That is, for a true step,
The remainder of the detected light flux at half wavelength (hereinafter referred to as "h '"
).

Although the above description is for the mark not covered with the resist as shown in FIG. 7, the above logic is almost applied to the mark covered with the transparent film such as resist or glass (PSG). it can. However, in the above logic, the amplitude reflectances φa and φb take into consideration the multiple interference between the transparent film and the mark surface, and the wavelength λ in Eq. (26) is the wavelength in the transparent film (the wavelength in the air is The value obtained by dividing by the refractive index of the transparent film).

In this embodiment, according to the above principle,
The step amount of the lattice mark MG is measured. That is, each of the phase difference detection circuits SA1, SA2, SA3 in FIG. 3 first has the respective light quantity signals, light quantity signals IAn, IAn obtained at the time of position detection.
A half amount Δ of the difference between the phase difference ΔAn and ΔBn between Bn and the reference signal Ims is calculated. Next, each phase difference detection circuit SA1,
In SA2 and SA3, the maximum value AMAX of both signals is set by the internal peak hold circuit and bottom hold circuit (not shown).
n, BMAXn, and minimum values AMINn, BMINn are detected, and the contrast γ of each signal is calculated from this. The contrast of both signals is the same unless there is asymmetry due to the step pattern, but if they are different, the average value is adopted.

Each phase difference detection circuit SAn further obtains the ratio β of the magnitudes of ψ N and ψ 0 from the contrast γ and the formula (20), and the β and the phase difference Δ and the formula (21) from ψ N and ψ 0 Find the relationship (as a complex number).

Each phase difference detection circuit SAn has the widths a and b of the concave and convex portions of the lattice mark MG and the period P, which are given by means of an operator's input from a console (not shown), for example. The values a'and b'are calculated using the values and the equations (14) and (15), and these are calculated using the equations (22) and (23).
To calculate the values (complex numbers) of φa and φb. Then, the phases ωa and ωb of φa and φb are calculated from the equations (24) and (25), and the difference ω is calculated as described above.

From the phase difference ω, it is of course possible to obtain the step h ′ from the equation (26) as described above. However, in the averaging circuit SS, each detection position correction circuit C
Since the weighted average weight of the detection position ΔXn ′ for each wavelength by An is determined based on the phase amount of each step difference amount with respect to each detection wavelength, the output value from each phase difference detection circuit SAn is The phase amount is more preferable than the step h ′. The phase amount δ is half (δ = ω / 2) of the round-trip phase amount ω of the step h ′. This phase amount δ is also the remainder with respect to the true phase amount with a phase difference (π) corresponding to a half wavelength of the detection light.

Of course, in the averaging circuit SS, the weighted average weight may be determined based on the step amount itself. In that case, the output value of each phase difference detection circuit SAn may be the step h '. . However, when the grating mark MG is covered with a resist or the like, the step h ′ obtained from the equation (26) is affected by the refractive index of the resist or the like (refractive index near the grating mark), but δ = ω / Since the relationship of 2 is not affected by the refractive index of the resist, it is better to perform the weighted average weighting based on the phase amount δ.

However, if the wavelength in vacuum is used as the wavelength λ when calculating the step h ′ by the equation (26), h ′ is not an accurate value as the step amount, but the same as the phase amount δ. Not affected by the rate. At this time, in the averaging circuit SS, the value of the detected step amount h ′ for each wavelength λn is
If the distance is close to λn / 4, a large weight is given, and if it is far from λn / 4, a small weight is given to average (weighted average) the detection positions by the respective wavelengths λn.

In the above step detection, the lattice mark MG has been described by taking a mark in which the boundary (sidewall) between the concave portion and the convex portion as shown in FIG. 7 is vertical as an example.
Even if the mark has a tapered side wall, it is of course possible to detect the position (step detection) with high accuracy. In this case, the widths a and b of the concave portion and the convex portion to be input are not a + b = P, but the mark step difference may be calculated based on the values of a and b as described above.

As is clear from the above description, this first
In the embodiment, the phase difference detecting circuit SAn constitutes the step detecting means, the phase difference detecting circuit SAn and the corresponding detection position correcting circuits CAn constitute the position detecting means, and the averaging circuit SS forms the calculating means. It is configured.

As described in detail above, according to the position detecting device and the position detecting method of the first embodiment, the "01th detection method" is adopted as the interference type alignment method and the two light quantity signals obtained are used. Not only can the position of the lattice mark be detected based on (the light amount signals of the first and second combined light fluxes An and Bn) as in the conventional case, but also the step (depth) of the lattice mark, more accurately, the detection accuracy. The step-equivalent amount that has a large effect on the step difference can be calculated as a remainder with respect to half the wavelength of the incident light beam (wavelength in the resist) at the step. (2m + 1) / 4 of the wavelength in the resist of
Whether or not it meets the condition of double, or the wavelength in the resist of the detection light is 4 /
It is possible to easily determine whether or not the condition of (2m + 1) times is satisfied.

Therefore, the detected light flux is set to a plurality of wavelengths, and the position detection and the step equivalent amount (remainder) are performed for each wavelength, and the calculated step is ¼ of the wavelength (in the resist).
By weighting the detection positions with a large weight for the detection positions at wavelengths close to twice and a small weight for the detection positions at wavelengths apart from ¼ times, the averaging effect of multiple wavelengths can be obtained. It is possible to perform the position detection with extremely high accuracy even if the lattice mark is maximized and asymmetric.

In the first embodiment described above, the case where the light beams having a plurality of wavelengths are simultaneously applied to the grating mark to detect the position is described. However, the present invention is not limited to this. By irradiating the mark MG with light fluxes of a plurality of wavelengths separately for each wavelength, the beams An and Bn of the components of the respective wavelengths may be received separately for each time. In this case, it is not necessary to separately provide a detector for receiving the first and second combined light fluxes for each wavelength, and the dichroic mirror 1 in the light receiving unit is not necessary.
It is also possible to omit 6 and 18, and it is also possible to process signals of a plurality of wavelengths by providing only one phase difference detection circuit SA and inputting light quantity signals of respective wavelengths to it in a time division manner. The advantage is that the light receiving optical system and the signal processing system can be simplified, and the device configuration can be significantly simplified.

However, in this case, the wavelength selection filter 12 is removed from the light receiving portion for the reference signal Ims, and the reference grating SG
It is necessary to make light beams of all wavelengths incident on. This is because, as described above, when only a specific one-wavelength light beam is incident,
This is because the reference signal Ims cannot be obtained when the wavelength is not irradiated (when the wavelength is detected by another wavelength).
However, in this case, it is not necessary to exactly match the positions of the interference fringes of each wavelength on the reference grating SG, and the correction amount ΔFXn is obtained for each wavelength λn in the above-mentioned baseline check, and the above-mentioned correction is performed. good. In addition, in order to irradiate each light flux in a time-division manner, each light source should be on-o in a short time.
It is desirable to use a semiconductor laser that is easy to ff.

On the other hand, in the method of irradiating light fluxes of a plurality of wavelengths at the same time as in the above-described first embodiment, and receiving light separately for each wavelength, the detection for each wavelength can be performed at the same time, so the measurement time can be shortened. There is an advantage.

In the first embodiment, in the step detection, the ratio of the magnitudes of ψN and ψ0 is calculated by the light amount signal IA.
The calculation is made from the contrast of n and IBn, but the present invention is not limited to this.
It is also possible to measure the light amount ratio itself of the Nth-order diffracted light and the 0th-order diffracted light and use the square root thereof.

As a method of detecting the light quantity ratio of the Nth-order diffracted light and the 0th-order diffracted light, for example, a shutter capable of blocking at least one of the light-transmitting beams ± LF is provided near the light flux selecting member 6 in FIG. After the above-described position detection is completed or before the start of the position detection, either one of ± LF is shielded by this shutter, and at this time, the detectors 17a, 17b, 19
a, 19b, 20a, 20b light intensity signal IA
Each intensity ratio of n and IBn may be obtained. In this case, since the number of beams incident on the grating mark MG is one for each wavelength, the respective light quantity signals IAn, In are obtained.
Bn has no beat and is a DC signal. When, for example, the transmitted light beam −LF is shielded by the shutter, only the 0th-order diffracted light by the grating mark MG of the transmitted light beam + LF is incident on the detectors 17a, 19a, and 20a, and the light amount signal IAn is at each wavelength. The light quantity of the 0th-order diffracted light is shown, and only the 1st-order diffracted light by the grating mark MG of the transmitted beam + LF is incident on the detectors 17b, 19b, 20b, and the light quantity signal IBn indicates the light quantity of the N-th order diffracted light at each wavelength. become.

Therefore, in the method of directly measuring the light quantities of the 0th-order diffracted light and the Nth-order diffracted light as described above, as compared with the above-described calculation method from contrast in which the uncertainty regarding the determination of the sign of the expression (20) remains, The magnitude ratio of ψ 0 can be measured more accurately.

In the above embodiment, in order to simplify the explanation, the rotating radial grating plate RR is used as the frequency shifter.
Although the case where G is used is illustrated, the present invention is not limited to this, and two acousto-optic modulators (AOMs) are used as frequency shifters, and a first Zeeman laser light source that oscillates at a central wavelength λ1 is used. A second Zeeman laser light source that oscillates at the central wavelength λ2 may be used as the light source.
Further, various dichroic mirrors may be replaced with a dispersing element such as a prism.

Further, in the above embodiment, the case where the detection lights of three wavelengths are used is illustrated, but the detection lights of arbitrary plural wavelengths are not limited to three wavelengths and may be used. When the number of wavelengths is further increased, the dichroic mirror 2 in FIG.
3 and the number of dichroic mirrors 16 and 18 and the number of detectors can be increased to easily cope with the problem.

In the first embodiment, when the heterodyne system in which the frequencies for the position detecting incident beams ± LF are made different is adopted, in other words, the grating mark and the interference fringe are relatively scanned in the periodic direction. The relative scanning means is a first of a pair of coherent light beams having different wavelengths.
The frequency of the second light beam is slightly different from the frequency of the second light beam, and the interference fringes formed thereby are moved by a constant velocity in the periodic direction on the grating mark (rotary radial grating plate). Although the case has been illustrated, the present invention is not limited to this. For example, incident beam ± L
Relative scanning in which the frequency of F is made equal (homodyne system) and the wafer stage WST is scanned in the detection direction at the time of position detection, and the grating mark and the interference fringes are relatively scanned in the periodic direction by the wafer stage WST. Means may be configured. Also in this case, each signal becomes a sine wave having an equal beat frequency proportional to the scanning speed of wafer stage WST, and the same detection as above can be performed. The homodyne method has an advantage that a frequency shifter (rotating radial grating plate RRG or the like) is not required and the light transmitting optical system is simplified.

On the other hand, in the heterodyne method, the wafer stage WST may be stopped and placed during detection. In addition to the high S / N ratio achieved by the heterodyne, the wafer stage WST
Need no control mechanism for scanning at constant speed,
Further, there is also an advantage that fluctuations (mainly air fluctuations) of outputs (LFG, LMG) of the laser interference system 22 that monitors the wafer stage WST position can be averaged during the detection.

<< Second Embodiment >> Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment relates to an exposure apparatus in which the position detection apparatus of the first embodiment described above is adopted as a so-called off-axis alignment detection system OFA.

The exposure apparatus according to the second embodiment includes a reticle stage RST that holds a reticle R in a horizontal plane substantially orthogonal to the optical axis AX of the projection optical system PL, and a projection optical system P.
A wafer stage WST that holds the wafer W on a surface conjugate with the reticle R with respect to L is provided. Therefore, the illumination system IO including the light source in a state where the reticle R and each shot area on the wafer W are aligned as described later.
When the reticle R is illuminated with the illumination light from P, the circuit pattern formed on the pattern surface of the reticle R is projected through the projection optical system PL at a predetermined reduction ratio (for example, 1/4).
Is transferred to the shot area on the wafer W.

Further, in this exposure apparatus, the off-axis alignment detection system OFA including the position detection apparatus 100 of the first embodiment described above is provided. This off-axis alignment detection system OFA is an optical axis A of the projection optical system PL.
The wafer W is irradiated with the detection beam in a plane parallel to the optical axis AX, which is separated from X by a predetermined distance.

Here, the reticle stage RST is slightly moved in the XY two-dimensional directions by the drive system (not shown) and the optical axis A.
The wafer stage WST is configured to be capable of minute rotation around X, and the wafer stage WST is two-dimensionally movable as in the first embodiment. The position coordinates of the wafer stage WST are measured by a laser interferometer 22 (not shown in FIG. 11, see FIG. 1).

Further, the wafer W is placed on the wafer stage WST via a not-shown θ stage and a wafer holder.

In this exposure apparatus, so-called baseline measurement is indispensable, and after this baseline measurement, a plurality of shot areas on the wafer W are provided at specific spots, for example, 10 shot areas. The position of the alignment mark composed of the lattice mark is detected, and the so-called least squares method is used from the data of these detected positions and the data of the design value of the mark to shift the position of the mark in the XY two-dimensional directions, rotate the wafer, The amount of expansion and contraction of the wafer is calculated, and the array coordinates of the shot areas are calculated using this calculation result and the design data of each shot area and stored in the memory.

In the actual exposure, the steps
Repeats stepping and exposure with the And Repeat method. During this stepping, each shot is positioned at the exposure position (within the exposure field of the projection optical system PL). At this time, two-dimensional movement of wafer stage WST is performed based on the shot arrangement coordinates stored in the memory, and each exposure shot is aligned with reticle R.

Here, the baseline amount is the reticle R
The projection point of the center CCr of the laser beam on the wafer side (which substantially coincides with the optical axis AX) and the off-axis alignment detection system O
It is nothing but the positional relationship in the X and Y directions between the FA detection center point Rf4 and the projection point on the wafer side. The positional relationship is such that the off-axis alignment detection system OFA itself detects the amount of positional deviation between the corresponding mark on the fiducial mark plate FP and the projection point of the detection center point Rf4, and the coordinate position of the wafer stage WST at that time. Can be found by detecting the laser interferometer 22. In the second embodiment, this baseline measurement is performed in the same manner as in the first embodiment, and the position according to the present invention described in the first embodiment is used to detect the alignment mark position of a specific shot on the wafer W thereafter. The detection method is used.

Therefore, according to the second embodiment as well, it is possible to detect the position of the asymmetric lattice mark attached to the shot area on the wafer W with extremely high accuracy, and to use the detection result, the so-called Since the array coordinates of the shot areas on the wafer W are calculated by the statistical processing by the least square method, and the alignment between the reticle R and each shot area on the wafer W is performed based on the array coordinates, it is expected that the alignment accuracy is improved. be able to.

In the second embodiment, the case where the position detecting device of the first embodiment is applied to the off-axis alignment detecting system has been described, but other through-the-lens (TTL) alignment detecting system and through-the-lens The position detection method and apparatus of the present invention can be similarly applied to a reticle (TTR) alignment detection system.

[0133]

As described above, according to the present invention,
In the "interferential alignment" with a plurality of wavelengths, it is possible to detect not only the position of the grating mark but also the step equivalent amount thereof. Then, weighting is performed according to the step equivalent amount, and the detection positions at each wavelength are weighted and averaged. It is possible to perform a weighted average by multiplying by, and it is possible to detect the position of the lattice mark with higher accuracy than in the case of the simple average.

[0134]

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a position detection device according to a first embodiment.

FIG. 2 is a perspective view showing how a diffracted beam is generated by a rotating radial grating plate.

FIG. 3 is a block diagram showing an example of a position detection circuit which constitutes the device of FIG.

4 (1) is a diagram showing a light amount signal IA1 of a light flux A1 having a wavelength λ1 which is an output of the detector 17a shown in FIG.
(2) is the light quantity signal IB1 which is the output of the detector 17b
And (3) is a diagram showing the reference signal Ims which is the output of the detector 15.

5 (1) is a diagram showing a light quantity signal IA2 of a light flux A2 having a wavelength λ2 which is an output of the detector 19a shown in FIG.
(2) is the light quantity signal IB2 which is the output of the detector 19b
And (3) is a diagram showing the reference signal Ims which is the output of the detector 15.

6 (1) is a diagram showing a light quantity signal IA3 of a light flux A3 having a wavelength λ3, which is the output of the detector 20a shown in FIG.
(2) is the light quantity signal IB3 which is the output of the detector 20b
And (3) is a diagram showing the reference signal Ims which is the output of the detector 15.

FIG. 7 is an enlarged view showing an example of a lattice mark MG.

FIG. 8: Diffracted light amplitudes ψ 0 and ψ N are amplitude reflectances φa and φb
FIG. 2 is a diagram showing the process derived from the above in polar coordinates of complex numbers, (1) is a diagram showing that the 0th-order diffracted light amplitude ψ 0 is determined from amplitude reflectances φa and φb, and (2) is amplitude reflection. A diagram showing that the first-order diffracted light amplitude ψ1 is determined from the ratios φa and φb. (3) is a diagram in which ψ0, ψ1 obtained from (1) and (2) of the same figure are written on the same polar coordinates. is there.

FIG. 9 is a diagram showing an example of a result of a simulation that is a cause of the idea of the present invention, in which (1) is a mark step h.
Where 50, 100, 150 and 200 nm are shown as abscissa resist thickness d [μm] and ordinate position detection error [μm], (2) shows mark step h of 250, 300, 350, 400
It is a figure which shows the result in the case of nm similarly to (1).

10 (1) is a diagram showing a cross section of a lattice mark which is a premise of the simulation result of FIG. 9, and FIG. 10 (2) is an enlarged diagram of one period thereof.

FIG. 11 is a diagram showing a configuration of a main part of an exposure apparatus according to a second embodiment.

[Explanation of symbols]

17a, 17b, 19a, 19b, 20a, 20b Detector (light receiving means) 100 Position detecting device 102 Light transmitting optical system W Wafer (substrate) MG Grating mark RRG Rotating radial grating plate (relative scanning means) SAn Phase difference detection circuit (step) Detection means, part of position detection means) CAn Detection position correction circuit (part of position detection means) SS averaging circuit (calculation means)

Claims (11)

[Claims] 1. A position for detecting the position in the periodic direction of a grid mark formed on a substrate on which a fine pattern is formed and having a periodicity (period = P) in a specific direction and repeating a concave portion and a convex portion. A detection method, wherein a plurality of pairs of coherent light beams having different wavelengths are incident on the grating mark, the period of the amplitude distribution is 2P / N (N is a natural number), and the period direction is the period of the grating mark. A first step of forming interference fringes equal to the direction and relatively scanning the interference fringes and the grating mark in the periodic direction; a first step of reflected / diffracted light of the incident light beam by the grating mark. A first combined light beam which is a combined light beam of the regular reflection light of the light beam and the Nth-order diffracted light of the second light beam;
And a second combined light beam that is a combined light beam of the specularly reflected light of the light beam and the Nth-order diffracted light of the first light beam,
And a second step of separately receiving light for each of the plurality of wavelengths;
A third step of detecting the position of the grating mark for each wavelength based on a change of the light amount signals of the first and second combined light fluxes for each wavelength due to the relative scanning; and a step corresponding to the step of the grating mark Based on the change in the light amount signals of the first and second combined light fluxes for each wavelength associated with the relative scanning and the design data of the lattice mark, the level difference of the lattice mark near the surface of the lattice mark. A fourth step of calculating each wavelength as a remainder divided by half of each wavelength of the incident light beam in the medium; and calculating the position of the grating mark detected for each wavelength for each wavelength. The amount equivalent to the step is
The closer to a quarter amount of each wavelength of the incident light beam near the surface of the grating mark, the more weighted the weighted average is, and the weighted average value is set as the final detection position of the grating mark. A position detecting method including a step. 2. In the first step, a plurality of pairs of coherent light beams having different wavelengths are time-divisionally incident on the grating mark for each wavelength, and the period of the amplitude distribution is 2P / N.
(N is a natural number) and an interference fringe whose periodic direction is equal to the periodic direction of the grating mark is formed for each wavelength, and the interference fringes for each wavelength and the grating mark are relatively scanned in the periodic direction. The position detecting method according to claim 1, wherein: 3. The position of the grating mark for each wavelength is detected by the first combined light flux and the second light flux associated with the relative scanning.
3. The position detecting method according to claim 1, wherein the detection position is obtained by averaging the detection positions obtained based on each phase of each change in the light amount signal of the combined light flux. 4. The calculation of the step equivalent amount is performed by calculating the ratio of the widths of the concave portion and the convex portion of the lattice mark, and the light amounts of the first combined light flux and the second combined light flux associated with the relative scanning. 4. The position detecting method according to claim 1, wherein the position detecting method is performed based on a phase difference of signal changes and a contrast. 5. The light quantity ratio between 0th order diffracted light and Nth order diffracted light reflected / diffracted by the grating mark is measured for each wavelength of the incident light beam, and the step equivalent amount is detected by the grating mark. On the basis of the ratio of the widths of the concave and convex portions, the phase difference between the light amount signal changes of the first combined light beam and the second combined light beam due to the relative scanning, and the measured light amount ratio. The position detecting method according to any one of claims 1 to 3, wherein: 6. A position detection for detecting the position in the periodic direction of a grating mark which is formed on a substrate on which a fine pattern is formed and which has periodicity (period = P) in a specific direction and which repeats concave and convex portions. A device for forming a coherent light beam on the grating mark so as to form an interference fringe having a period of amplitude distribution of 2P / N (N is a natural number) whose period direction is equal to that of the grating mark. A light-transmitting optical system in which a plurality of pairs of light beams having different wavelengths are incident;
First combined light beam that is a combined light beam of the specularly reflected light of the second light beam and the N-th order diffracted light of the second light beam, the specularly reflected light of the second light beam, and the Nth time of the first light beam. Light receiving means for photoelectrically converting the second combined light beam, which is a combined light beam with the folded light, separately for each of the plurality of wavelengths; and for relatively scanning the grating mark and the interference fringe in the periodic direction. Relative scanning means; Position detection for detecting the position of the grating mark for each wavelength from the change in the light amount signals of the first and second combined light fluxes for each wavelength obtained by the light receiving means due to the relative scanning. A change in the light quantity signal of the first and second combined light fluxes for each wavelength obtained by the light receiving means, which is caused by the relative scanning, and design data of the grating mark. Based on the Step difference detecting means for calculating for each wavelength as a remainder divided by half of each wavelength of the incident light beam in the medium near the surface of the grating mark; the position of the grating mark detected for each wavelength, The closer the step-equivalent amount calculated for each wavelength is to the quarter-equivalent amount of each wavelength of the incident light beam near the surface of the grating mark, the more weighted the weighted average, the average value is obtained. Position detecting device having a calculating means for determining the final detected position of the. 7. The position detecting means calculates an average value of detection positions obtained based on respective phases of respective light amount signal changes of the first combined light beam and the second combined light beam due to the relative scanning. The position detecting device according to claim 6, wherein the position detecting device detects the position of the lattice mark. 8. The step detecting means changes the ratio of the widths of the concave portion and the convex portion of the lattice mark, and changes in the light amount signals of the first combined light beam and the second combined light beam due to the relative scanning. 8. The position detecting device according to claim 6, wherein the step equivalent amount is calculated based on the phase difference and the contrast. 9. The apparatus further comprises a light quantity ratio measuring means for measuring a light quantity ratio of 0th-order diffracted light and N-th order diffracted light reflected / diffracted by the grating mark for each wavelength of the incident light beam, and detecting the step. The means includes a ratio of respective widths of the concave and convex portions of the lattice mark, and a phase difference between light amount signal changes of the first combined light flux and the second combined light flux due to the relative scanning,
The position detecting device according to claim 6 or 7, wherein the step equivalent amount is calculated based on the light amount ratio obtained by the light amount ratio measuring means. 10. The position detecting device according to claim 6, wherein the relative scanning unit is a stage capable of scanning the substrate in the periodic direction of the lattice mark. 11. The relative scanning means causes a frequency of a first light beam and a frequency of a second light beam to be slightly different from each other among a plurality of pairs of coherent light beams having different wavelengths, 10. The position detecting device according to claim 6, further comprising means for moving the interference fringes formed thereby on the grating mark in a periodic direction at a constant speed.